In facilities, such as a data center and the like, an information processing system is built, in which multiple information processing apparatuses are connected through a network as servers. Power consumption of the information processing apparatuses becomes larger as the number of arithmetic processing units (for example, central processing units (CPUs)), and memories (memory modules) increases. Accordingly, in recent years, demands are on the rise for saving power of overall facilities including a plurality of information processing apparatuses, that is to say, suppressing power consumption in an information processing system. Hereinafter an information processing apparatus is referred to as a “server”, and an arithmetic processing unit is referred to as a “CPU” for the sake of convenience. Facilities are referred to as a “data center”.
Currently, most CPUs are provided with a power saving function. The power saving function is normally achieved through an operation setting (C state), in which at least a part of operation in a CPU is stopped, or a performance setting (P state), in which at least one of the power source voltage of a CPU and the operating frequency (clock frequency) of the CPU is changed. In recent years, such a power saving function is used in order to control the amount of power consumption in an information processing system that is built in facilities.
In the operation setting, an internal clock through CPU software, an internal clock through hardware, and all the internal clocks may be selectively stopped. Accordingly, the amount of power consumption of a CPU may be suppressed in accordance with a range of an internal clock to be stopped.
The amount of power consumption of a CPU becomes larger as the operating frequency (clock frequency) becomes higher, and also as the power source voltage becomes higher. Accordingly, power consumption of a CPU may be increased or decreased by the performance setting.
There are some information processing systems that perform control in order to keep the total amount of power consumption at a certain value or less using the power saving function of a CPU. One of the related-art information processing systems that control the amount of power consumption using the power saving function of a CPU is provided with a management apparatus that manages power distribution to a plurality of information processing apparatuses, and respective information processing apparatuses.
A priority for suppressing power consumption is set to each of the information processing apparatuses. The management apparatus actually monitors the amount of power consumption of each of the information processing apparatuses, accumulates the amounts of power consumption, and subtracts the accumulated value from the upper limit value of available supplies of power so as to calculate the amount of surplus power. If a larger amount of power is demanded, each of the information processing apparatuses makes a request to the management apparatus for an additional amount of power. If the management apparatus receives a request for an additional amount of power exceeding the amount of surplus power from one of the information processing apparatuses, the management apparatus decreases, using the power saving function of the CPU, the amount of power consumption of an information processing apparatus having a lower priority than the information processing apparatus that has requested the additional amount of power. In this manner, if the management apparatus is not allowed to distribute the amount of power that is additionally requested, the management apparatus ensures the requested amount of power by decreasing the amount of power consumption of an information processing apparatus having a lower priority, and further allocates the additionally requested amount of power to that information processing apparatus. Accordingly, the management apparatus effectively uses the amount of power up to the upper limit value while suppressing the total amount of power consumption in the information processing system not higher than an upper limit value, and allows the entire performance of the information processing system to improve.
In this related-art information processing system, the amount of power consumption of the information processing apparatus is decreased by a change in the operation setting. In the suppression on the amount of power consumption by a change in the operation setting, at least the supply of an internal clock to the CPU core is stopped, and operation of the CPU core is stopped. Accordingly, the processing capacity of the information processing apparatus whose amount of power consumption is to be reduced is significantly decreased. Thus, execution by the CPU core of various programs including an application program (hereinafter abbreviated as an “application”) is stopped.
Each of the information processing apparatuses included and operated in the information processing system is normally run in order to execute processing requested individually. Accordingly, although there is a difference in priority (level of importance), it is often not desirable for the running information processing apparatus to stop execution of a program requested for the processing.
A related technique is disclosed in Japanese Laid-open Patent Publication No. 2010-123071, for example.